1. Field of the Invention
The present invention is a closure means for well conduits in the form of an internal bidirectional tubing plug. The plug prevents well fluids from passing the plug in either direction in a well conduit until the plug is activated and pumped apart, and the pieces that comprise the plug are either pumped down or up a tubing string or down or up a casing or tubing annulus of the well or fall to the bottom of the well. The plug is activated or deconstructed in situ through application of hydraulic pressure on the top side of the plug.
2. Description of the Related Art
The present invention relates to closure means for well conduits. More particularly, it relates to temporary plugs that are removable without mechanical intervention from the surface above the well. Plugs are used to run new or used tubing, known as a work string, into a well filled with well fluids, usually drilling mud or water. The tubing is run behind a drill bit and drill collar, behind a packer or open ended as fast and as safely as possible. As the tubing is run into the well, the displaced well fluid is directed to a pit or tank while preventing the well fluid from entering the tubing, through a bit, a packer, or through an open end.
It is also desirable to prevent displaced well fluids from being displaced out the surface open end of the tubing into the atmosphere. The displaced well fluids will take the path of least resistance to the atmosphere. If the displaced well fluids are allowed to enter the tubing, well fluids will “spray” out the surface open end of the tubing. This spray of well fluids will coat the rig, rig crew, stripping rubber, blow out preventers, wellhead, and the ground and will generally impair safe working conditions. The spray may also contaminate the ground or create a fire or chemical hazard since some well fluids contain hazardous chemicals and compounds.
In general practice the tubing is lowered very slowly into a well to allow the well fluids to drain from the tubing/annulus casing valve, and slow enough to prevent well fluids from spraying out the open end of the tubing. This method of running a tubing string very slowly is costly to well operators due to the additional rig time. It is desirable to run the tubing as fast as possible, in a safe manner, to reduce the well operators cost.
One problem is controlling the well fluids from being displaced from the tubing/casing annulus while the tubing is being lowered into the well. This is accomplished by using a “stripping rubber”, as known in the art. The stripping rubber effectively seals the tubing/casing annulus diverting all displaced well fluids up the tubing and out the casing valve at the same time. The casing valve is generally placed on a kill-choke/spool below the blow out preventers. The casing valve is generally opened to a flow line ending at a flow back tank, frac tank, and or an earth pit. The flow lines that are directed to a flow back tank generally have sufficient restriction in them to not be able handle all of the displaced well fluids through the casing valve which causes more of the displaced well fluids to be directed into the tubing and out the end of it at the surface.
A second problem is that if the well operator chooses to run a stripping rubber and a drill pipe float valve above the bit, i.e. essentially a check valve, all displaced well fluids will be diverted to the casing valve and to a tank or pit. But using a drill pipe float valve causes another problem.
A third problem is that when using a drill pipe float valve and stripping rubber circulation of the well fluid may only occur down the tubing and up the tubing/casing annulus. There are situations where this setup may limit the control of the well by not allowing well fluids to be circulated down the tubing/casing annulus and up the tubing.
A fourth problem is that when using a drill pipe float valve with a stripping rubber and drilling out any obstructions in a well such as DV tools (known as stage cementing tools), DV rubbers, primary cementing rubbers and any excess cement left in the well, a high circulation rate is necessary to carry all drilled and washed debris up the tubing/casing annulus through the casing valve, flow line, and to a wash tank. If the casing valve or flow line become plugged circulation up the tubing/casing will be lost. If circulation is lost the annulus debris in the annulus will fall down hole around the tubing “sticking” the tubing. To remove the tubing a “fishing” job is required that is very expensive and for this reason this set up is not used by prudent operators.
A fifth problem is created when using a wire line (also known as “slick line”) retrievable “blanking plug”. One way to prevent well fluids from entering the tubing is to run a wire line retrievable blanking plug in a tubing nipple at or above the bottom end of the tubing. A retrievable blanking plug seals off fluid flow in both directions of the tubing. With a blanking plug in place while running the tubing, in conjunction with a stripping rubber, all displaced fluids are diverted through a casing valve. While picking up a new or used work string and running it into the well, there will be mill scale, rust, dirt, tubing dope, and all manner of debris that will fall down the tubing and land on top of the blanking plug.
Once the tubing is at depth the tubing is filled with fluid to equalize differential pressure across the retrievable blanking plug so that it may be removed from the tubing. This is accomplished by running a wireline blanking plug retrieval tool, and in some cases, an equalizing prong, to release the retrievable blanking plugs latching members from a tubing sub known as a nipple. However, in most cases tubing debris, as mentioned above, have fallen down and covered the retrievable blanking plug such that the retrievable tool and equalizing prong cannot engage the blanking plug to equalize, release, and pull it from the tubing to the surface. At this time the debris must be washed off the retrievable blanking plug before it is pulled from the tubing. This may be accomplished by using coiled tubing and or snubbing operations or other methods, which incur additional cost and time. Sometimes the fluid laden tubing must be pulled from the well. Experience has shown that using a retrievable blanking plug is not a cost effective way to prevent well fluids from entering a tubing string.
A sixth problem occurs when running a “pump-out-plug”. The pumped-out portion of the pump-out-plug has an outside diameter greater than the internal diameter of the tubing, and therefore, it may not be circulated out of the well up the tubing. Further, the outside diameter of the pumped-out portion of the pump-out-plug is generally of a dimension that prevents is from being circulated from the well up the tubing/casing annulus. Additionally the pumped-out portion of a pump-out-plug is normally made from a metal, generally aluminum, which will fall on top of any cased-hole tools below the pump-out-plug and prevent them from being pulled from the well at a later date. The metal pumped-out portion may become wedged between the casing internal surface and the outer surface of the cased-hole tools (known as retrievable packers, retrievable bridge plugs, and others). Therefore, in general, pump-out-plugs are only run in a well at the bottom end of a tubing string, sometimes below a retrievable packer, and the pumped-out portion of the pump-out-plug falls into the rat hole at the bottom of the well. Pump-out-plugs are not compatible and with a drill bit.
A seventh problem occurs when running a “rupture disk”. A rupture disk is run above the bit and drill collars in the tubing in a tubing nipple or a J-J (the small internal area in a tubing collar between the two pin ends of tubing) to prevent well fluid from entering the tubing when it is run into a well that is full of well fluid. When it is time to establish circulation the tubing is filled with fluid and pressure applied on top of the rupture disk, thereby rupturing it and establishing circulation in the well. The debris left in the J-J or tubing nipple of the rupture disk are protrusions into the internal diameter of the tubing string. These protrusions may hang debris circulated up the tubing and plug it off, causing the operator to pull the work string. Many times surface intervention may be required to pierce the rupture disk to facilitate rupturing it. Experience has shown that the use of a rupture disk is fraught with potential problems and unnecessary expense.
An eight problem occurs when lowering tubing into a well with drilling mud that contains lost circulation material, such as cotton seed hulls, walnut chunks, cellophane particles, etc. Experience has shown that the lost circulation material, when entering the bit, may plug it off, or may plug off the tubing above the bit. This situation reminds us that under these circumstances it is generally a good idea to run some type of tubing plugging apparatus.
The present invention addresses these problems. A primary object of the present invention is to prevent well fluids from entering the tubing as it is lowered into a well full of fluid.
A second object of the invention is to remove the plugging apparatus with well fluids leaving no debris in the tubing.
A third object of the invention is to remove the plugging apparatus without surface intervention.
A fourth object of the invention is to be able to establish circulation at any time, allowing the operator full control of the well.
A fifth object of the invention is to allow the well operator, when pumping out the plugging apparatus, to monitor the tubing pressure at the surface, to identify when the internal bidirectional tubing plug has released by observing a pressure build up and fall off, and then establish that the well is circulating.
A sixth object of the invention is to leave the internal diameter of the tubing constant when the plugging apparatus is removed.
A seventh object of the invention is to blank off the tubing with very small parts that may be circulated through a workover bit, up the tubing/casing annulus, or through the workover bit up the tubing to the surface.
An eighth object of the invention is to manufacture the small parts of this plugging apparatus from material recognized as biodegradable.
A ninth object of this invention is to manufacture the internal parts of this plugging apparatus of a material that is sufficient for the pressures and temperatures encountered in most well conditions.
A tenth object of this invention is to manufacture the parts of this plugging apparatus from a material that is easily drillable.